1. Field of the Invention
The present invention relates to a driving support apparatus for a vehicle, the driving support apparatus making a braking control for avoiding collision against a control subject, such as a vehicle ahead, when the vehicle determines that the possibility of collision of the vehicle against the control subject is high.
2. Description of the Related Art
A large number of driving support apparatuses for vehicles performing various vehicle controls has conventionally been proposed. The driving support apparatus of this type recognizes a driving environment in front of the vehicle by a camera or a laser radar device mounted to the vehicle, extracts an obstacle or a three-dimensional object such as a vehicle ahead from the driving environment data as a control subject, and performs various vehicle controls based upon a relative relationship between the extracted control subject and the vehicle.
As the vehicle control in the driving support apparatus of this type, there has been proposed a technique of setting a collision avoidance limit based upon a relative speed between the vehicle and the control subject, and making a braking control by using an automatic brake when the relative distance between the vehicle and the control subject becomes not more than the collision avoidance limit, whereby damage upon the collision against the control subject can be reduced. For example, Japanese Unexamined Patent Application Publication No. 2007-223582 describes a technique of setting an enlarged braking region closer to the vehicle than an actual braking region specified by the collision avoidance limit, and making a preliminary braking control by using the automatic brake even before the vehicle goes into the actual braking region.
In the execution of the braking control described above, a three-dimensional object having a height not less than a set value from a road surface is generally selected as a control subject. Therefore, even if a falling three-dimensional object whose size from the road surface is small is present on the road in front of the vehicle, this object is not extracted as the control subject, and the braking control for this object is not performed.
However, when a three-dimensional object such as a falling object is present on the road in front of the vehicle, a driver generally decelerates the vehicle to pay attention to the object, and it is desirable to make some braking control for the object of this type in order to allow the behavior of the vehicle to conform to the driver's feeling.
On the other hand, when the braking control equivalent to the braking control for the vehicle ahead is made for an object whose size from the road surface is small, excessive braking force might be applied against the driver's intention. Accordingly, the control might be unnatural, in fact.